And yet, they're still not ISIS terrorists. The state of emergency was used to stop public discourse and dissent - both anarchists and non-anarchists were banned from attending marches during the Paris climate summit.
The police had to protect the COP21 and the visit from more than 150 head of states. They also have to protect administrations, newspaper offices, jewish organizations and others potential terrorist targets. There's just not enough police forces to handle all this, plus marches and anarchist protests
Not having proper resources isn't a reason to infringe upon the freedoms of the people. If the police can't handle their work, then they should just ignore less important crimes and focus their efforts on the stuff that matters. Otherwise the French government could use a lack of resources as an excuse to silence whoever they want. With a justification like that, they could make arrests for thought-crime.
Who's more of a threat to the public - random candle-throwing anarchists, or the heads of state of the biggest and most militarised and industrialised nations in the world?
Terrorists are terrorists regardless of affiliation. ISIS doesn't have organized operations in the west it just takes credit for lone acts.
By and large its not clear ISIS actually wants people to commit terror attacks in the west since it gets potentially useful recruits killed not fighting for territory in the middle East (note they are big on how you should definitely move to the ISIS territories).